Lubricating grease composition



United States Patent 3,386,916 LUBRICATING GREASE COMPOSITION Howard D.Moore, Chester, Norris A. Scarlett, Eastham, Wirral, and John A. Jones,Ellesmere Port, England, assignors to Shell Oil Company, New York, N.Y.,a corporation of Delaware No Drawing. Filed June 28, 1965, Ser. No.467,728 Claims priority, application great Britain, July 1, 1964,

64 9 Claims. (Cl. 252-21) ABSTRACT OF THE DISCLOSURE Greases useful in anon-oxidizing atmosphere comprising a lubricating oil base gelled togrease consistency with an inorganic gel coated with a surfactant ofesterifying and polymerizable silicon compounds and containing 110% of aC metal soap and 110% of an alkali or alkaline earth metal nitrite.

This .invention relates to lubricating grease compositions, particularlyto grease compositions gelled with inorganic gelling agents and isparticularly concerned with the improvement of the lubricatingproperties of such greases during operation in a non-oxidizingatmosphere.

It has been found that the lubrication of metal surfaces by conventionalinorganic greases under non-oxidizing conditions, for example thelubrication of metal bearings in the helium atmosphere of an atomicreactor, results in severe pitting of the metal surfaces and a resultantpremature failure of such bearings. This failure is believed to be dueto an oxide layer, normally present on the bearings surface, beingabraded away. Under normal oxidizing conditions, such as is obtainedwhen running in air, this oxide layer would be rapidly replaced, but ina nonoxidizing atmosphere this replacement does not occur andconsequently the-re is premature bearing failure.

It has now been discovered that this difficulty can be overcome to agreat extent by the incorporation in the inorganic lubricating grease ofa boundary lubricant additive to minimize the abrasion of the oxidelayer and an oxygen-yielding compound to react with the metal surfacesto be lubricated and renew the oxide layer.

Accordingly, a lubricating grease has been developed consistingessentially of a lubricating oil base, an inorganic gelling agent andsmall amounts each of (a) an alkali or alkaline earth metal salt of analiphatic monocarboxylic acid having from 10 to 22 carbon atoms and (b)an alkali or alkaline earth metal nitrite. It is found that theselubricating grease compositions successfully reduce bearing failureunder non-oxidizing conditions and that they also exhibit adequateradiation stability and high-temperature performance.

Examples of the alkali and alkaline earth metal salts of aliphaticmonocarboxylic acids, hereinafter referred to as soaps, which are usedas boundary lubricant additives in the grease compositions of thepresent invention are sodium stearate, potassium stearate, lithiumstearate, lithium oleate, sodium oleate and calcium stearate. Thesesoaps may be employed in concentrations between 1% and 10% by weight,more preferred concentrations being between 3% and 7% by weight based onthe final lubricating grease composition.

Of the alkali or alkaline earth metal nitrites which may be used asoxygen-yielding compounds for the purposes of this invention, sodiumnitrite is preferred. Concentrations of nitrites are between 1% and 10%by weight, more preferred concentrations are between 2% and 7% by weightbased on the final lubricating grease composition.

As has already been stated, the grease compositions of the presentinvention are those containing an inorganic gel material and comprise abase lubricating oil which is thickened to a grease consistency 'bymeans of such an inorganic gel material. This inorganic gel is in theform of an organo gel, that is to say one in which water has beendisplaced from a hydrogel of the gel material by a volatile organicliquid, such as an alcohol which, unlike the water of the hydrogel, issoluble in the base lubricating oil employed. Of the inorganic gelmaterials which may be used, amorphous inorganic colloids are generallysuit able, silica being especially useful because of its low cost andready availability. The organo gel should contain between 0.5% and 10%by weight of the inorganic gel material, preferably between 1% and 7% byweight. The preparation of such organo gels is disclosed in US. Patent2,986,518.

It is well known that lubricating greases comprising simply alubricating oil and an inorganic colloid tend to break down in thepresence of water. One. method of improving the water resistance of thegrease suitable for use in connection with the present invention is tocoat the particles of the organo gel material with a surface-activeagent such as an esterifying or polymerizable silicon compound.Particularly suitable polymerizable or esterifying silicon compounds forthis purpose 'are the alkyl alkoxy silanes, for example the mono-, diortri-me-thyl tri-, dior mono-methoxy or -alkoxy silanes. It is preferredto incorporate a surface-active agent when mixing the organo gel and thehot lubricating oil, or to incorporate'the surface-active agent with theorgano gel and/or the oil before such mixing. Other ingredients may alsobe added, in this way, for example an anti-oxidant such as phenylalphaor-beta-na-phthylamine, preferably added to the oil before mixing. Detailsof the method of mixing the organo gel and the base lubricating oil arealso disclosed in US. "Patent 2,986,518.

In order to provide the lubricating grease compositions of thisinvention with a satisfactory resistance to water, especially under theinfluence of neutron radiation as is necessary when such compositionsare used in atomic piles and nuclear power units, the surface-activeagent (surfactant) should be present in an amount between 15% and 400%by weight of the dry inorganic gel material. In general the quantity ofsurface-active agent necessary will be between 50% and 250% of theweight of the dry gel material.

The base lubricating oil which is used in present grease compositionsmay be any of the oils of lubricating grade which are commonly used ingrease manufacture. The oil may be refinedor semi-refinedparaflinic-,naphthenicor asphaltic-base mineral lubricating oil or a syntheticlubricating oil having a viscosity of from about 50 to 4000 SUS at F. Ifdesired, a blend of oils of suitable viscosity may be employed insteadof a single oil, by means of which a desirable viscosity Within therecited range may be secured. A particularly suitable tyPe oflubricating oil for use in high-temperature greases is residual oil,usually known as bright stock."

The invention will now be illustrated by the following examples:

EXAMPLE I A base lubricating grease composition was prepared tmaintained at a temperature of 200 C. by the use of electrical heaters.The flow rate of inert gas through the bearings and pressure vessel wascontrolled at 10 cc. per minute. Failure was indicated by increase innoise of the I 5 bearings. havmg the formulauon' Perc t wt Tests carriedout under 300 lbs. axial load were limited Silica en 5 to 500 hours toensure that bearing failure was not due to "7 "f. e. f I e eDimethyldiethoxysilane (150% silica) 7.5 3:3 fatlgu The noniwl i j of ab anng qt i/ C. and run at 300 s. axial load is somewhat overPhenyl-alpha-naphthylamine 1.0 0 High viscosity index nvr oil having aviscosity of 10 Q 650 ecs Redwood Index at 140 F 86 5 The inert gas usedfor the test, was helium and this 5 gas was purified so as to containless than 1 part per To this base lubricating grease were added 5% byweight million of oxygen and less than 2 parts per million of each ofsodium nitrite and sodium stearate, at ambient water.

TABLE I Grease Atmos- Load Duration of Test Reason for failureComposition phcre in hours Base grease 300 lbs. axial 209, 21, 140, 90,168, S1 itti f composition. Helium {5 lbs. radial 304, 70, 120, 168. lia til s rid t g ti lessor extent the inner race of bearing. Example IHelium I} 500 (4 tests) No failure.

3001b 1 24 hlrs. rutnrtiing s.ax1a 500 i s. s ic Example I Hehum {5 lbs.radial.--..{500 ru hning No tests Example II Helium 500 No failure.

Example III Helium {g g giggi kzj 500 No failure.

temperature, by mixing into the grease with a spatula on As alreadystated, the grease compositions of the presa steel plate followed bymilling through a triple roll out invention, while successfully reducingbearing failure paint mill. The sodium nitrite was added as a 40% weightunder non-oxidizing conditions, also retain good radiation suspension inoil, the composition of the suspension stability. The composition ofExample I and the base being: lubricating grease alone (known to haveadequate radia- L g Water Trace tron stability) were tested by thefollowing procedure and the results are shown at Table II. It can beseen that a sodlum mmte Percent re' se co'n *osition of this 'nveriondoes show ood ra- Calcium di(C C alkylsalicylate) percent Wt 1.6 i a z 1A calcium sulfonate percent wt 6.4 40

MVI (neutral) oil having a viscosity of 170 secs, R dj ti test procedureRd 0 dx t 0F Balance e W 0d c a 14 t 40 cc. (4 x 10 cc.) of the greasecomposition under test The grease PIIOT t0 the addlhoh 0f the Sodiumhltflte and were contained in four glass tubes (15 cm. x 17.5 cm.).stearate had an IP penetration (worked) of 264 and a Irradiation was,inthe form of beta-rays from a 4 m.e.v. p Phlht of greater than 9 Thefinal g linear accelerator operating at 3 m.e.v. The dose rate regreasecomposltloh had an IP Pfihetratlon of ceived by the grease was 2 or 3megarads per minute. 291 and a drop point of 285 C. TABLE H EXAMPLE IIGrease Composition Raacliatlion, Pe etra P Drop The base lubricatinggrease composition of Example I 1 Ta S Nl containing 5 We1ght of sodiumstearate and 2% weight Base grease composition of Sodium nitrite. Thefinal grease composition in accor Example 3o ance with the invention hadan IP penetration of 258. 1 S88 EXAMPLE in The base lubricatin greasecomposition of Example I D0 containing 5% weight of sodium nitrite and5% weight 1,000 of lithium stearate.

The compositions of Examples I to III and the base We Clalm F Invention:lubricating grease of these examples were tested by the A lubricatinggfl' t C0ml10S{t10l1 0h$1Shhg essenfollowing procedure, the resultsbeing shown in Table I. lf 0f a lubricating base 011 thlckehed greasfi Td consistency by means of (2) an inorganic gel, (3) 1-10% est proce ureby Weight, basis total composition, of a salt of (a) a The testapparatus comprised essentially a pressure C1042 aliphaticmonocarboxylic acid, and (b) a metal vessel through which a suitableinert gas could be passed. selected from the group consisting of alkaliand alkaline A 0.25 horsepower motor was incorporated in said pres- 5earth metals, and (4) 1-10% by weight, basis total comsure vessel. Themotor shaft was supported at each end position, of a nitrite salt of ametal selected from the of the vessel by means of ball bearings (20 mm.X 47 group consisting of alkali and alkaline earth metals.

mm. x 14 mm. all steel) which were lubricated with 2. A lubricatinggrease composition consisting essenabout 4 grams each of the greasecomposition under test. tially of (1) a lubricating base oil thickenedto grease The bearings were fitted with pressed steel cages and theconsistency by means of (2) an inorganic gel, (3) ll0% races and ballsmade from SAE52100 grade steel espeby weight, basis total composition,of a salt of (a) a cially heat-treated to withstand high operatingtempera- C aliphatic monocarboxylic acid, and (b) a metal tures. Thehearings were run at 1450 rpm. under an selected from the groupconsisting of alkali and alkaline applied load of either 300 lbs. axialand 5 lbs. radial (the earth metals, (4) l-l0% by weight, basis totalcomposilutter being the rotor weight) or 5 lbs. radial only, and 7tion,, of a nitrite salt of a metal-selected from the group consistingof alkali and alkaline earth metals, and (5) 50-250% by weight, basisdry inorganic gel, of a surfactant selected from the group consisting ofesterifying and polymerizable silicon compounds.

3. A lubricating grease composition consisting essentially of (1) alubricating base oil thickened to grease consistency by means of (2) aninorganic gel, (3) 37% by weight, basis total composition, of a salt of(a) a C1042 aliphatic monocarboxyl acid, and (b) a metal selected fromthe group consisting of alkali and alkaline earth metals, (4) 27% byweight, basis total composition, of a nitrite salt of a metal selectedfrom the group consisting of alkali and alkaline earth metals, and (5)50-250% by weight, basis dry inorganic gel, of a surfactant selectedfrom the group consisting of esterifying and polymerizable siliconcompounds.

4. A lubricating grease composition consisting essentially of (1) alubricating base oil thickened to grease consistency by means of (2) aninorganic gel, (3) 1-10% by weight, basis total composition, of a saltof (a) a C aliphatic monocarboxylic acid, and (b) a metal selected fromthe group consisting of alkali and alkaline earth metals, (4) 1-10% byweight, basis total composition, of sodium nitrite, and (5 50250% byWeight, basis dry inorganic gel, of a surfactant selected from the groupconsisting of esterifying and polymerizable silicon compounds.

5. A lubricating grease composition consisting essen tially of (l) alubricating base oil thickened to grease consistency by means of (2)05-10% by weight, basis total composition, of an inorganic gel, (3)1-10% by weight, basis total composition, of a salt of (a) a C1042aliphatic monocarboxylic acid, and (b) a metal selected from the groupconsisting of alkali and alkaline earth metals, (4) 1-10% by weight,basis total composition, of a nitrite salt of a metal selected from thegroup consisting of alkali and alkaline earth metals, and (5) 50- 250%by weight, basis dry inorganic gel, of a surfactant selected from thegroup consisting of esterifying and polymerizable silicon compounds.

6. A lubricating grease composition consisting essentially of (1) alubricating base oil thickened to grease consistency by means of (2) 17%by weight, basis total composition, of an inorganic gel, (3) 110% byweight, basis total composition, of a salt of (a) a C1042 aliphaticmonocarboxylic acid, and (b) a metal selected from the group consistingof alkali and alkaline earth metals, (4) 1-10% by Weight, basis totalcomposition, of a nitrite salt of a metal selected from the groupconsisting of alkali and alkaline earth metals, and (5) 50-250% byweight, basis dry inorganic gel, of a surfactant selected from the groupconsisting of esterifying and polymerizable silicon compounds.

7. The lubricating grease composition of claim 2 in which the surfactantis an alkyl alkoxy silane.

8. The lubricating grease composition of claim 7 in which the surfactantis dimethly diethoXy silane.

9. A lubricating grease composition consisting essentially of (l) alubricating base oil thickened to grease consistency by means of (2)05-10% by weight, basis total composition, of an inorganic gel, (3)1-10% by weight, basis total composition, of a sodium salt of a C1042aliphatic monocarboxylic acid, (4) 110% by weight, basis totalcomposition, of sodium nitrite, and (5) 50-250% by weight, basis dryinorganic gel, of an alkyl alkoxy silane.

References Cited UNITED STATES PATENTS 2,514,331 7/1950 Morway 252212,563,606 8/1951 Kimberlin et al. 25228 2,648,633 8/1953 Peterson et al25228 2,986,518 5/1961 Carswell et al 25228 3,227,651 1/1966 Peterson25221 DANlEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner.

